Although the prevalence of dental caries in children is continuing to decline, a sizable minority remain significantly affected so as to account for a major portion of caries morbidity found in U.S. children. Identification of such children prior to the onset of caries is of considerable importance, so that risk can be reduced or eliminated. The long-term objective of this project is to perfect a caries risk- assessment model which could be used for the targeting of caries- preventive activities on an individual or group basis, as well as in clinical research. This model would be the precursor of a sage and effective battery of tests for caries risk assessment in children. Our underlying hypothesis is that there is a group of specific laboratory and clinical positive (pathogenic) or negative (protective) caries risk factors which can be used to accurately assess the risk of caries onset. The present proposal is for a continuation of NIH/NIDR grant R01-DE08946 which commenced two years ago. The specific aims are: (1) to refine a model for assessment of dental caries risk in children who were initially clinically caries-free, (2) to develop and test a model for the assessment of dental caries risk in children who have become caries active during the study, and (3) to continue to isolate and preserve a library of mutants streptococci isolates from the existing study population for parallel studies (funded by other means) involving molecular genetic approaches which may contribute to our understanding of virulence characteristics, and which may enhance the efficiency of future versions of the risk assessment model. The models involve combinations of measures identified from our previous and ongoing studies, including salivary mutans streptococci, lactobacilli, calcium, phosphate, and fluoride, plaque accumulation, prior exposure to fluoride, and demographic data. Exceptionally encouraging results to date strongly suggest that accurate and clinically useful caries risk assessment may be a reality in the near future. Preliminary risk assessment models correctly identified children who developed caries with sensitivities of 92% and 84% in fluoridated and fluoride-deficient communities respectively. Specificities were 78% and 73% respectively. The proposed study is an extraordinary opportunity to obtain unique longitudinal clinical and laboratory data from an already- assembled group of children, which would span the time between eruption of their permanent teeth and their pre-teen years. A four-year continuation of the current study, involving our existing population of approximately 500 nine year-old children, will facilitate the further development and refinement of a caries-risk assessment model. The continuation will enable subjects to have been followed for up to six years, and will provide a unique opportunity to investigate longitudinally the natural history of caries initiation and progression, and the interactive roles of a number of the pathogenic and protective caries risk factors described above. The data will be employed in the development of a risk assessment model through the use of logistic regression and discriminant analyses.